Modeling of Coulomb blockade devices and circuits with random structures

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Since Coulomb blockade takes place in tunnel junctions with very small capacitance, devices utilizing this phenomenon must have very small structures. Accordingly, experimental devices of nowadays often have random structures. In this study Coulomb blockade device circuits with two-dimensional irregular array of fine metallic particles deposited on an insulator film.The nearest neighbor fine metallic particles pair forms a tunnel junction. A system which is formed from the fine metallic particles, dots, is modelled as follows. The system of the dots is assumed to have regular two-dimensional grid structures and the randomness is taken into account by the random values of capacitance and resistance of each junction. Above the dots a gate electrode is placed, and capacitances are formed between the gate and the dots. These values are set by regular random numbers generated in compute. Critical charge for each tunnel junction is obtained by a program to use in the circuit simulation based on the orthodox theory. The influences of the difference between the cases of regular and random capacitances on the electrical characteristics are esamined.